Scriptable is an iOS app which allows you to place widgets like News, Stocks, etc. but it allows to place your own code. nostr:npub1nxzp3zn90r44z07aeajc7wyah4fju49c9d3g45mxvmm64rmnrdusffch7m wrote a few widgets and that's how I learned to play with them from his repo.

You can do a lot in javascript.

https://video.nostr.build/5ab2114e586e5e80d1859d1acd92ed1c29b0082dae445c4b448122e627a973e5.mp4